Water tanks for aircraft include a tank main body composed of a cylinder and domes disposed at both ends of the cylinder.
A known cylinder of such a water tank for an aircraft includes a laminate of an inner liner made of thermoplastic resin, a plurality of fiber-reinforced resin layers formed by winding reinforced fiber impregnated with thermosetting resin on the outer peripheral surface of the inner liner, and a honeycomb core layer disposed between the fiber-reinforced resin layers (See Japanese Unexamined Patent Application Publication Nos. 2007-268929A and 2011-245796A).
The cylinder of the water tank for an aircraft is provided with a tank port for taking water and air in and out.
The tank port is provided through a through-hole formed in the cylinder.
The through-hole interrupts the fiber of the fiber-reinforced resin layers and the honeycomb core layer in the tank port region of the cylinder, resulting in a decrease in strength for the internal pressure of the water tank for an aircraft.
Conventionally, the region around the tank port in the water tank for an aircraft is reinforced by filling the honeycomb core layer with a filler called a potting compound and curing the filler, and by disposing reinforcing sheets made of glass fiber between the core layer and the fiber-reinforced resin layers.
Unfortunately, the potting compound used for filling the core layer is expensive. The reinforcing sheets are disposed between the core layer and the fiber-reinforced resin layers while the reinforced fiber impregnated with thermosetting resin is wound on the outer peripheral surface of the inner liner, i.e., during filament winding. This work is complex and takes time.
Filling the core layer with the potting compound increases weight, which needs to be improved for a reduction in weight.